Like topaz vis-à-vis quartz

• More puzzling, as a crossword
• Less cushiony
• Less of a picnic
• Higher on the Mohs scale
• Less giving
• Less simple
• More solid

WordNet Word definitions in WordNet
adj. not easy; requiring great physical or mental effort to accomplish or comprehend or endure; "a difficult task"; "nesting places on the cliffs are difficult of access"; "difficult times"; "a difficult child"; "found himself in a difficult situation"; ...

Wikipedia Word definitions in Wikipedia
Harder may refer to: Harder (surname) Harder, Washington , unincorporated community, United States Harder (fish) USS Harder Harder Kulm Harder Stadium